74-17 HLC
Evaluation of the
New York State
Dual-Catalyst
Vehicle
November 28, 1973
Test and Evaluation Branch
Emission Control Technology Division
Environmental Protection Agency
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Background
Dr. William Balgord of the New York State Department
of Environmental Conservation contacted the Emission Control
Technology Division to request low mileage evaluation of a
dual catalyst control concept. Testing of the vehicle was
arranged and conducted in June of 1973. Subsequent to this
evaluation the vehicle was returned to New York State personnel
for mileage accumulation. After compiling approximately
25,000 miles on the dual catalyst system, Dr. Balgord again
brought the vehicle to the EPA Ann Arbor test facility for
evaluation.
System Tested
This dual-catalyst system employs Gould reduction
catalysts (model Gem. 67) for control of oxides of nitrogen
and Engelhard oxidation catalysts (model 2B) for control of
hydrocarbon and carbon monoxide. The reduction catalysts are
located forward of the oxidation catalysts in the exhaust
system. To facilitate quick attainment of system operating
temperature and good cold start emission control,two techniques
are employed. First,the distributor timing is modulated for
cold start. During starting normal ignition timing for the
engine is set. Immediately upon engine start up the timing
is retarded and employed for about two minutes before switching
back to the normal ignition setting. To allow this timing
modulation a dual point distributor system is used in con-
junction with manual switching. While manual switching was
employed in the prototype vehicle,production vehicles would
utilize an automatic timed solenoid. The second technique
involves start-up modulation of injection air. During the
first two minutes of operation following cold start air is
injected at the exhaust ports in front of the reduction
catalysts. This injection leads to oxidation both in the
exhaust manifold and in the reduction catalyst. After two
minutes the exhaust port air is shut off and only normal
air injection in front of the oxidation catalysts is employed.
Again, on the developmental system air switching is accomplished
manually but in production this manual function would also
be replaced with an automatic timed solenoid.
The system as tested employed conventional carburetion
calibrated to give a relatively constant carbon monoxide
level of between 2 and 3 percent. Lean excursions of the
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carburetor have been minimized through careful bench calibra-
tion. Since proper system performance depends on operation
within this carbon monoxide band,frequent calibration based
on barometric pressure (air density) is required. (One
planned test at the EPA was canceled due to excessively
low barometer.) In production this sensitivity could be
alleviated through the use of barometric pressure compensated
carburetion techniques.
The vehicle used for this system demonstration was a
1972 American Motors Matador equipped with a 304 CID eight
cylinder engine and an automatic transmission. The vehicle
was tested at a 3500 pound inertia weight.
Mileage Accumulation and Vehicle Maintenance
The dual catalyst system was operated by New York State
personnel for 25,000 miles over a period of about 5 1/2 months
in both city-suburban and highway situations. It is not
possible to assess the equivalency of this accumulation
procedure with the current certification driving schedule.
Lead-free Amoco premium gasoline (as marketed in the eastern
United States) was used exclusively for this mileage accumu-
lation. New York State personnel reported that mileage
accumulation will continue.
In general, maintenance on the vehicle followed that
recommended by American Motors for its 1972 automobiles
and did not specifically follow current certification pro-
cedures. As previously noted carburetor adjustments were
frequently made to facilitate emission testing under varying
barometric conditions.
Test Program
All testing was performed in accordance with the 1975
Federal emission test procedure as specified in the
November 15, 1972, Federal Register (and appropriate sub-
sequent modifications). Testing and vehicle operation required
the use of unleaded gasoline.
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A total of five emission tests were run at the EPA
laboratory in Ann Arbor, Michigan. The first was conducted
in June of 1973 when the catalytic system was at low mileage.
Early in November of 1973 the vehicle was tested twice after
approximately 25,000 miles had been accumulated on the system,
During that testing starting problems attributed to poor
choke and inadequate driver operation were encountered. The
vehicle was returned in mid-November after a comprehensive
tuneup for retest. Two additional tests were run at that
time. The first of these latter two tests was voided by a
CVS operation error.
Fuel economy for the second and third series of tests
has been calculated using the carbon balance technique.
For comparative purposes the 1972 Federal emission test
procedure has also been used to calculate fuel economy.
Test Results
Table I illustrates the 1975 composite emission results
obtained during the EPA testing. Also presented are fuel
economy data calculated using the 1972 Federal emission
test results and the carbon balance technique,
During tests #2 and #3 the vehicle stalled or false
started several times during the cold start. This poor
performance stemmed from inadequate choking and driver
operation and led to relatively high hydrocarbon emissions.
Test #4 after tuneup was characterized by good starting
performance. This test demonstrated emission levels near the
1976 statutory limits.
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Conclusions;
1. At low system mileage the New York State dual-
catalyst vehicle met the 1976 statutory levels.
2. Excluding tests which were characterized by cold
starting problems^ after 25,000 miles the dual-
catalyst system is still operating near the 1976
statutory levels.
3. Fuel economy measured was 11% poorer than for a
comparable 1973 AMC vehicle but only 3% poorer than
for a comparable 1974 AMC vehicle. The test vehicle
was a converted 1972 AMC vehicle, but no fuel economy
data for a comparable unmodified 1972 AMC vehicle
is available.
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Technical Assessment
The New York State dual-catalyst system closely parallels
the type of systems reported by Gould and other manufacturers
at the EPA hearings early this year. There are no significant
technological differences employed by New York State except
that the Gould catalyst utilized by New York State does not
represent the latest generation of Gould catalysts. The
vehicle did display good emission control for 25,000 miles
of system operation as contrasted to the unfavorable evaluations
reported earlier to EPA by manufacturers.
After meeting with New York State personnel and analyzing
the data presented in this report, the EPA technical staff
still considers their previous assessment of the dual-catalyst
approach as valid. Relatively tight control of air-fuel
ratio is required mandating the use of advanced carburetion
with air density compensation. The latest test data as
reported here indicates that after 25,000 miles of operation
the NOx control has deteriorated and is near the statutory
limit. Previous information available concerning the Gould
system would suggest that rapid deterioration of NOx control
after 25,000 miles would also be expected to occur for the
New York State system. New York State personnel plan to
continue mileage accumulation and subsequent data would be
useful for verifying the deterioration rate.
While the successful demonstration of 25,000 miles of
emission control at the 1976 statutory standards indicates
the importance and potential of continuing research and
development of the dual-catalyst approach, a single success-
ful test does not indicate that the dual-catalyst approach
is ready for implementation on new vehicle production.
In his July 30, 1973, decision the Administrator concluded
that "...although the Gould catalyst has shown by far the
best durability results of any (reduction) catalyst to date,
more work on matchina the catalyst to the engine and on
improved fuel metering, accompanied by extensive durability
testing, will be required before it will be ready for
widespread vehicle use". The data obtained through the
testing of the New York State vehicle does not materially
change the data base from which the Administrator drew
his July 30 conclusion.
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Table I
New York State Car
Ann Arbor EPA Testing
1975 FTP 1972 FTP
Date Test # Odometer Mileage HC CO CO? NOX MPG
6/6/73 1 28039 0.33 2.99 ~ 0.11
11/1/73 2 49035 1.02 3.37 746.5 0.40 11.2
11/2/73 3 49048 0.68 3.22 731.3 0.32 11.4
11/23/73 4 49175 0.37 1.67 751.4 0.47 11.2
1976 Statutory Standards 0.41 3.4 — 0.40
Average 3500 Ib 1973 vehicle — —• — — 13.9
1973 AMC 3500 Ib 304 CID (1 vehicle) — — ~ — 12.6
1974 AMC 3500 Ib 304 CID (2 vehicles) —- -- — — 11.6
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